1. Field of the Invention
The present invention relates to the field of shock load detection equipment, and more particularly but not by way of limitation, to a shock load detection device for mounting on a computer disk drive unit for detecting a mechanical shock load imposed thereon and issuing a write-fault signal to stop the writing of read/write heads.
2. Discussion
Heretofore it is to be expected that a mechanical shock load can generate errors in the performance of a computer disk drive unit. If a mechanical shock occurs during a read operation, the read error resulting causes an error from the error detection circuitry. If the shock occurs during writing, the standard circuitry now used for error detection must reread the data written on the disk. Also, if a shock occurs, the read/write heads can move off track, destroying written data.
Production disk drive units now detect a mechanical shock by sensing when a servo head is driven off track. This sensing method is imperfect because the indication of a shock may come too late to prevent a write error. Further, the shock may cause a data head position error without any servo head position error detected Also, an off track error in the servo signal can occur for other reasons besides a mechanical shock.
As disk drive storage units become more compact and therefore more susceptible to error caused by shock and vibration, customer specifications also become more stringent. Therefore it becomes increasingly desirable to provide a shock detection system for a computer disk drive unit used in storing and reading data thereon.
Takewo Chiku, et al, U.S. Pat. No. 3,304,787 taught a three-dimensional accelerometer device using piezo resistive materials. The accelerometer is mounted on a moving body to be measured. A common intersection either coincides with a point on or within the moving body and is positioned adjacent another point whereby acceleration or deceleration exerted on or adjacent the common intersection point can be measured either in magnitude or direction.
Jones, et al., U.S. Pat. No. 4,088,907 taught the use of a piezo-electric acoustic emission device. The device is responsive both to compressional wave energy and to shear/wave energy from any direction along an x, y, and z axis so that the source of the acoustic emission may be determined.
In U.S. Pat. Nos. 3,363,471 to Lovelace, et al.; U.S. 3,853,000 to Barnett, et al.; 4,658,175 to Albert, 4,498,025 to Takahashi, 4,644,181 to Mosconi, et al.; and 3,137,834 to Pfann: various types of tranducers, accelerometers and measuring devices using piezo-electric crystals are described for measuring forces along three axial directions.
None of the above mentioned prior art devices provide the unique features and novel structure of the present invention as described herein.